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Can't adjust shift cables in both forward and backward on a pre alpha drive

R

Royall

Member
This thing is driving me nuts..

I have a pre-alpha drive with a 120 mcm Mecruiser. I just bought the boat second hand and knew it had problems with backward shifting. Thought it was just an out of adjustment thing so I took it anyway.

I follow the manual and do this:

Setting the adjustment nut at 6 inches of the lower shift cable when in full forward gear.
Then I adjust the control cable accordingly. But I can only adjust it so it works neutral/forward or adjust it for neutral/backward but not backward/neutral/forward together. It's like one or the other...

The adjustment gab is even so big that I can even adjust it so both gears won't grab and both backward and forward will rattle.

The cables look fine, and I really don't know what to do now. I don't have a trailer so working on the drive is gonna be a problem.
I read a lot about replacing the lower shift cable, but why should that be the problem when I can move the engine in gear by pushing and pulling the cable by myself. Only backwards shifting requires some force if done by hand (Forward is doable with just a little push).

It feels like the lower shift cable needs more travel in both directions to make it work.

Anyone?
 
Two possible issues come to mind.
Cable is worn/stretched or,
Shift spool is worn in lower gear case.

Back in the day of the 120 drive they used a bronze based shift spool and it wore out. Not necissarily the spool itself but the end of it and now to much slack exists.

Try this,
Adjust the 6 inch demension smaller.
By doing this you will gain some additional travel at the shift spool.

Remember!!! The smaller that demension the more suceptable shifting will will cause over travel and possibly activate shift interuptor switch when shifting into gear.

If shorting 6" to 5 15/16" does not help. Refer to my first couple comments.
Less than 5 15/16" most likely cause interrupter switch activation
 
kghost said:
Two possible issues come to mind.
Cable is worn/stretched or,
Shift spool is worn in lower gear case.

Back in the day of the 120 drive they used a bronze based shift spool and it wore out. Not necissarily the spool itself but the end of it and now to much slack exists.

Try this,
Adjust the 6 inch demension smaller.
By doing this you will gain some additional travel at the shift spool.

Remember!!! The smaller that demension the more suceptable shifting will will cause over travel and possibly activate shift interuptor switch when shifting into gear.

If shorting 6" to 5 15/16" does not help. Refer to my first couple comments.
Less than 5 15/16" most likely cause interrupter switch activation
Click to expand...

I will test a shorter dimension!
Is there a way to test the lower cable to check if it is still ok?

Also I took off the plastic end part of the cable and if I'm correct I can see that someone cut something off from the inner core cable. Not sure how much though...
 
Hard to explain but I`ll try. Remove the drive, and examine the shift components for any looseness or damage
Shift the drive into full fwd, the brass shoe should be exactly at 12:00 holding the prop shaft tight in a counterclckwise rotation attempt to turn the brass shoe . There should be almost no movement . Excess movement indicates a worn shift spool,
Do you have the actual merc manual?
 
Based on age of cable, it would say its over 20 years old....
That possibly combined with a worn shift spool....
It needs some expert hands on review!!
 
the manual in the earlier post i dont think covers that info on length.

I am also not sure you should be wasting time on it.
I would suggest replace with new.

I am not on my home pc so dont have acess to older manuals right now to see what the length should be.
 
kghost said:
the manual in the earlier post i dont think covers that info on length.

I am also not sure you should be wasting time on it.
I would suggest replace with new.

I am not on my home pc so dont have acess to older manuals right now to see what the length should be.
Click to expand...

Yeah well, have to order the cable, the nut tool, the thread tap and hire a trailer :( That's going to cost.. Lets hope it's the cable...
 
Well maybe think about buying a boat in this century....

Your dealing with what, 40+ year old boat?

Hope you weren't expecting it to be like new!!

Myself, I have replaced at least 1000 short cables and most werevon far newer boats than yours!
 
Most insist on a on water test run to make sure everything is working, those that dont buy as is and fix whats wrong before going into the water
 
kghost said:
Well maybe think about buying a boat in this century....

Your dealing with what, 40+ year old boat?

Hope you weren't expecting it to be like new!!

Myself, I have replaced at least 1000 short cables and most werevon far newer boats than yours!
Click to expand...

I was thinking because if I take the lower shift cable of the backet and use it by hand I can put it in forward gear really easy and smoothly. Backwards is another story because I need to pull pretty hard and also hear a lot of rattleling. Also when trying to pull it in reverse you can feel that the cable is trying to push back. Am I on the right track to think this is something more than just a cable?

Cheers
 
You are doing it wrong.
You cant test with engine running properly.

You should be spinning prop by hand to allow ****ing.

I really would suggest finding someone who understands shifting and cable and shift spool issues.

You are kind of troubleshooting this blindly.

A functioning cable and or shift spool will appear good when testing the way you are doing it. Once cable is adjusted and mounted all that testing means nothing.
Your issue is NOT the ability to shift. It is the ability to get into gear with the system/parts you have, (brackets, cable adjustments/shift spool)
 
kghost said:
You are doing it wrong.
You cant test with engine running properly.

You should be spinning prop by hand to allow ****ing.

I really would suggest finding someone who understands shifting and cable and shift spool issues.

You are kind of troubleshooting this blindly.

A functioning cable and or shift spool will appear good when testing the way you are doing it. Once cable is adjusted and mounted all that testing means nothing.
Your issue is NOT the ability to shift. It is the ability to get into gear with the system/parts you have, (brackets, cable adjustments/shift spool)
Click to expand...

Allright I have my boat on a trailer on the parking lot near my house. Pulled the drive and checked things out. I noticed shifting by rotating the ram on the lower unit by hand does make it shift easy in both directions so I guess it's not the spool.

A new shifting cable set should arrive tomorrow so that's done.
Edit: I can see a retaining nut at the shifting cable at the aft side. Does that mean it already has a new style conversion?

Also there is some kind of oil inside my shaft bellow. Could also be a mixture of water and grease but it is rather thick. Wouldn't surprise me because the large gasket fell apart when I pulled the drive so it was really old. Something to check?
 
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If the lower brass shoe is NOT in a straight line with the prop locked CCW then there is spool play
Do the test procedure because you cant tell by just shifting by hand

Edit: I can see a retaining nut at the shifting cable at the aft side. Does that mean it already has a new style conversion?

Yes, if its a mercruiser one the plastic tube will unscrew CCW once the inner core is removed


Also there is some kind of oil inside my shaft bellow

any oil is from a bad yoke seal that need to be replaced

What manual do you have?
 
Bt Doctur said:
If the lower brass shoe is NOT in a straight line with the prop locked CCW then there is spool play
Do the test procedure because you cant tell by just shifting by hand

Edit: I can see a retaining nut at the shifting cable at the aft side. Does that mean it already has a new style conversion?

Yes, if its a mercruiser one the plastic tube will unscrew CCW once the inner core is removed


Also there is some kind of oil inside my shaft bellow

any oil is from a bad yoke seal that need to be replaced

What manual do you have?
Click to expand...

What is the correct procedure to check this?

I have Service Manual Number 4, Stern Drive Units MCM 120 - 260 Sections 1 thru 7

This is the current situation:
shift-prop-lock.jpg
 
Last edited:
If those two pictures are your shift shaft then your spool is NOT the issue.
12:00 oclock with forward engagement.
10:30 ish for reverse engagement.

So what is left is a few other things to check.

1. Vertical shift shaft in gimbal housing. At bottom, Upside down U shape must be very tight to bronze shaft in pictures. If U is bent or bronze piece is too loose then that is an issue. U needs to be restored, and or bronze piece needs to be replaced.

2. Look at bell crank on top of vertical gimbal housing shift shaft. Is roller wheel intact and not worn away? May need replacement.

3. Either or both primary shift cable and short shift cable are worn and to much slack/play in cable and they need replacement.

Good clean pictures of 1 & 2 would be good to see.

3. Manual has test measurements to see if cables are bad.
 
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kghost said:
If those two pictures are your shift shaft then your spool is NOT the issue.
12:00 oclock with forward engagement.
10:30 ish for reverse engagement.

So what is left is a few other things to check.

1. Vertical shift shaft in gimbal housing. At bottom, Upside down U shape must be very tight to bronze shaft in pictures. If U is bent or bronze piece is too loose then that is an issue. U needs to be restored, and or bronze piece needs to be replaced.

2. Look at bell crank on top of vertical gimbal housing shift shaft. Is roller wheel intact and not worn away? May need replacement.

3. Either or both primary shift cable and short shift cable are worn and to much slack/play in cable and they need replacement.

Good clean pictures of 1 & 2 would be good to see.

3. Manual has test measurements to see if cables are bad.
Click to expand...

Thanks for the checklist will do that next!

Currently I'm trying to remove the old shift cable from the bellhousing... And yeah, I'm totally screwed at the moment.
The brass nut was so tight my wrench rounded off the nut till a point the socket spins freely around the nut having no grip :(

Tried almost everything.. Nut oil, even heat from my propane torch..
I was able to hit with a flathead screwdriver in a 45 degrees angle to try and hammer the bolt CCW but it's just stuck, veeery stuck. My guess is some kind of locktite or something thats why I tried heat. I even hammered off a piece of the nut and thinking about drilling it out in the hopes I won't screw the bellhousing threads. Pfff...

shift-nut.jpg
 
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run a tap thru it if the threads are beyond repair I have a procedure to repair them.
The correct tap is 1/4 x 18 NPST
NOT A 1/4 INCH PIPE TAP
 
Next time you encounter a stuck fastener like this, drill the nut. Start with the smallest drill you can just to get a hole going. If you have a Dremel and can get a 1/16 drill in there that's best. drill into the top edge of the nut into one of the points where you have the most meat. Gradually go bigger until there's more hole than metal. Now take a sharp chisel and give it a whack where the hole is. This should split the nut right at the hole, expand it slightly to form a C shape and break loose any thread locking compound. This should minimise damage to the thing the nut is threaded on to.
 
Bt Doctur said:
run a tap thru it if the threads are beyond repair I have a procedure to repair them.
The correct tap is 1/4 x 18 NPST
NOT A 1/4 INCH PIPE TAP
Click to expand...

Thanks, I was thinking about doing that if it was too damaged.
Luckily the threads are still fine after testing mounting the new shift cable and it still threads in firm.
Can finally continue today!
 
o2batsea said:
Next time you encounter a stuck fastener like this, drill the nut. Start with the smallest drill you can just to get a hole going. If you have a Dremel and can get a 1/16 drill in there that's best. drill into the top edge of the nut into one of the points where you have the most meat. Gradually go bigger until there's more hole than metal. Now take a sharp chisel and give it a whack where the hole is. This should split the nut right at the hole, expand it slightly to form a C shape and break loose any thread locking compound. This should minimise damage to the thing the nut is threaded on to.
Click to expand...

Thank you very much, that indeed sounds like a better procedure. Should really consider buying a good dremel for the future!
 
kghost said:
If those two pictures are your shift shaft then your spool is NOT the issue.
12:00 oclock with forward engagement.
10:30 ish for reverse engagement.

So what is left is a few other things to check.

1. Vertical shift shaft in gimbal housing. At bottom, Upside down U shape must be very tight to bronze shaft in pictures. If U is bent or bronze piece is too loose then that is an issue. U needs to be restored, and or bronze piece needs to be replaced.

2. Look at bell crank on top of vertical gimbal housing shift shaft. Is roller wheel intact and not worn away? May need replacement.

3. Either or both primary shift cable and short shift cable are worn and to much slack/play in cable and they need replacement.

Good clean pictures of 1 & 2 would be good to see.

3. Manual has test measurements to see if cables are bad.
Click to expand...

The U shape rod and the roller looked fine. I reinstalled the new shift cable and put the drive back on.
Had someone spin the prop in forward gear while I pushed the plastic end inwards. I measured for 6 inches but that's not possible... I can rotate the adjustment barrel all the way in but even then I miss a few mm's...

It's really weird because I have put the inner core wire all the way in the plastic end and also made sure it was deep enough so I can also see the core at the little hole thats at the top of the plastic end piece. What is going on...
 
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